package src.com.changli.d_for;

import java.util.Scanner;

public class Demo2Sum {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int sum1 = 0;
        int cnt1=0,cnt2=0;
        int sum2 = 0;
        for(int i=1;i<=n;i++){
            if((i&1)==1){
                cnt1++;
            }
            else {
                cnt2++;
//                sum2+=i;
            }
        }

//        System.out.println(cnt1);
        System.out.println(cnt2);
    }
}
